| |
 |
 |
Since 1978
Published in Sarov (Arzamas-16), Nizhegorodskaya oblast |
RUSSIAN FEDERAL
NUCLEAR CENTER -
ALL-RUSSIAN RESEARCH INSTITUTE
OF EXPERIMENTAL PHYSICS |
|
 Русский |  English
|
ON A MODE OF IDEAL GAS PLANAR LAYER EXPANSION INTO VACUUM
V. E. Shemarulin, S. S. L'vova, Yu. V. Yanilkin
VANT. Ser.: Mat. Mod. Fiz. Proc 2015. Вып.3. С. 46-63.
We have discovered and investigated in detail the class of exact solutions of the gas dynamic equations that describe the isentropic ideal gas expansion into vacuum, when the gas fills a finite-thickness plane layer, in the case of specifically preset initial distributions of gas-dynamic parameters at the adiabatic index of 3.
As an example, the particular case with the zero gas initial velocity, while the initial density velocity, in accordance with quadratic law, turns into zero on the gas-vacuum interface. Characteristic features of the solution and its connection with the Legendre polynomial are highlighted. The obtained particular solution can be used for testing the techniques and programs for numerical solving the gas dynamics problems. The following specifics of a numerical method can be checked when this solution is used as a test: degree of the entropy preservation in isentropic flows, accuracy of the flows description in the vicinity of weak and strong discontinuities on the vacuum interfaces. Additional information on the numerical method accuracy can be obtained by the verification of main quality properties of exact solutions in numerical solution: immobility of sound points (weak discontinuity points), immobility of flow boundaries up to the known time, vacuum line movements (gradient catastrophe curves) under the known law.
The results of the numerical solution for the problem in question obtained with the EGAK technique are presented. Keywords: 1D gas dynamics equations, ideal gas, isentropic expansion into vacuum, exact solutions, numerical solution.
| MODELING OF RADIATION DEFECT ACCUMULATION IN PURE MOLYBDENUM USING THE METHODS OF KINETIC THEORY AND CLASTER DYNAMICS
M. Yu. Romashka, A. V. Yanilkin
VANT. Ser.: Mat. Mod. Fiz. Proc 2015. Вып.3. С. 64-75.
The modeling of radiation defect accumulation in thin pure molybdenum films under the effect of ion radiation was studied. Two approaches to the modeling were used: kinetic theory with mean cluster size and cluster dynamics.
The paper discusses the limitation of the first approach applicability. It can be inapplicable in the cases when defect clusters are generated in the cascades of atom shifts and the cluster diffusion to the drains, such as the surface, intergrain surfaces and dislocations, is present. This is due to the fact, that it is impossible to take into account the cluster distribution by size in the frames of the kinetic theory and to assign personal diffusion coefficients to each cluster size.
In the case of cluster dynamics the obtained results are in good agreement both with the experiment and the calculations by other authors. At that the proposed method of cluster dynamics realization differs from those used before: a stochastic approach to the cluster dynamics based on the SPPARKS code is implemented. The advantages of the stochastic approach are such as the algorithm simplicity, simplicity of reactions setting in SPPARKS, as well as high stability as compared to the standard approach, where the system of big amount of differential equations is solved. The main drawback of the approach is the limited reagent concentrations at the bottom. Keywords: kinetic theory, cluster dynamics, ion irradiation, thin films, molybdenum, point defects, SPPARKS.
|
[ Back ] |
|
|
| |
| |
 |
| |
|